SURFACE AND DEEP HYDROLOGY OF THE NORTHERN ATLANTIC-OCEAN DURING THE PAST 150000 YEARS

The abrupt shifts in foraminiferal delta(18)O observed in core ODP 609 (the meltwater signature of the Heinrich events, see Bond et al. 1992 b, 1993) are seen in ten North Atlantic high sedimentation rate cores; the decreasing south-west to north-east gradient is well pronounced. This confirms that the Heinrich events are associated with major surge s of the Laurentide ice sheet, when it is believed approximately 10(6) km(3) of ice are liberated during each event. A tentative reconstruct ion of the changes in surface and deep-water density, based upon the s tudy of cores SU 90-39 (53 degrees N 22 degrees W) and SU 90-08 (43 de grees N 30 degrees W), is presented. To calculate the density of surfa ce water, sea surface temperature is obtained using a foraminiferal tr ansfer function (see CLIMAP 1981) and salinity is estimated using the foraminiferal delta(18)O record corrected for the temperature effect o n isotopic fractionation. The density of deep water is directly derive d from the benthic delta(18)O record, after corrections for the mean g lobal changes in Ocean delta(18)O. Results indicate that the North Atl antic Ocean has been repetitively a potential area of deep-water forma tion during the last glacial period.